Aircraft & RV Grounding

[mjobee]

In aircrafts, rv's, autos etc..., the metal frame acts as a "conducting ground" or as some state "an artificial ground". How does that work to dissipate lightning, line surges & other potential high voltage issues. I understand a building's electrical system is connected to the earth to diisipate lighting, line surges, unitentional contact with higher voltage liens, & to stabilize voltage to ground. And bonding connects the effective ground fault current path to the service grounded conductor to clear a ground fault. But how does an electrical system that is not connected to the earth, such as an aircraft, dissipate high voltage occurances such as lightning?

 

[LarryFine]

A vehicle on rubber tires can indeed develop static charges, which is why they ground and bond planes before refueling. Toll-booth lanes usually have static-discharge wires because toll-takers were getting shocks from drivers.

However, in most vehicles, which are basically separately-derived systems, the chassis is the reference for ground, and any difference between it and the outside world is largely not relevant. Plus, atmospheric humidity often helps.

 

[hurk27]

Not in aircraft but in Rv's, Auto's Truck's, Etc... The purpose of using the body and frame as a ground is more for saving wire, at least this was the original concept, after computers started being added to control the engines, it was found that having parallel paths of current was causing many I/O errors and computer problems, and now we see that they have isolated most bonding to the frame and body to prevent this. it is still bonded but in one place only, to the engine block. but this bond is the second reason, it is to allow the opening of fuses. these are the only two reasons that the frame/body was bonded to.

Lightning uses the air as a conductor, if the body of a vehicle is in this path through the air, then lightning will see this path as a lower resistance, lightning cares less if the electrical inside of the vehicle is bonded to the body or not, lighting only wants to complete its path to earth.

To help with this higher content of carbon was added to tires to help dissipate static, and lightning, static at a gas pump could be bad for your health


I'm a little rusty on aircraft, but I do know they did at one time bond the systems to the air frame, but I think this was discontinued as having a fuse fail just because a wire made contact with the air frame was too dangerous, and if I remember right they now an isolated system with grounding monitors, so the system will still function, but can be fixed on the next landing.

as for lightning it's the same as a vehicle body, the body of an aircraft, is just a lower resistance path in the air that lightning can pass through hopefully without damage, they do bond many parts of the air frame together, but this is only to ensure, good conductivity of the lightning current, like an equal-potential bonding system we use around pools.

Electrical current does not need or require a bond to earth to function.

 

[mjobee]

"Electrical current does not need or require a bond to earth to function."
Yes I agree that current flow does not need a bond to earth to function. And I think you answered my qustions which was "But how does an electrical system that is not connected to the earth, such as an aircraft, dissipate high voltage occurances such as lightning?" in that lightning will pass through least resistive path back to ground. Thanks for you help.

 

[hurk27]

Ok this is quit a question, and one in my area of my some what limited knowledge:grin:

First you have to understand, current does not take the least resistive path back, it shares all paths, with current dividing across these path proportionally to each path's impedance.

Lighting is not what many think, even though it had a DC potential , it is basically an high frequency AC event, if you have ever studied about HF AC, then there are two things to keep in mind about lightning, in your question would be "skin effect", the other is "resonate wave length"

if an aircraft is struck by lightning, almost all the energy is dissipated across the outer shell of the air frame, just like in a Faraday cage, the rest of the current, (DC to very low frequency) is dissipated in the metal as a conductor, (thus why they bond all the metal parts in the air frame together but not to the electrical system) this allows the lightning to pass right around the craft through the skin and frame and out the other side without damage (again hopefully) as we all know if there is a weak link it will find it. this is another reason why they went to more of an isolated electrical system (isolated from the air frame) to prevent any stray currents from entering the aircraft's electrical system. of course magnetic shielding would also come into play as, any high current AC can induce a current into conductors of another system, just like when we pick up ghost voltages on UN terminated wires that run in the same conduit or cable with conductors that have current on them. I would expect in a lightning strike this induced current could be quit sever, and how they shield from this I have no idea,

But for the most part look up about a Faraday cage, I think if you can understand how this works, you would have a better understanding of your question.

 

[nakulak]

I find the use of the word dissipate to be confusing.

lightning is the result of the potential differnce between upper atmosphere and earth. if the plane is in the path, lighting conducts through or around the plane. since the outer shell of the plane is usually conductive, some lighting conducts through and around. sometimes planes are damaged, sometimes not. since most planes actively attempt to fly around active areas, exposure is somewhat limited to accidental contact.

 

[hurk27]

I find the use of the word dissipate to be confusing.

lightning is the result of the potential difference between upper atmosphere and earth. if the plane is in the path, lighting conducts through or around the plane. since the outer shell of the plane is usually conductive, some lighting conducts through and around. sometimes planes are damaged, sometimes not. since most planes actively attempt to fly around active areas, exposure is somewhat limited to accidental contact.

If we were talking about a dynamic current source, I would agree, with using the term dissipate, but lightning is a charge, like a battery, and the current does dissipates?

Also there are other forms of lightning then cloud to ground, ground to cloud.
aircraft also have the problem of getting in-between the clouds or storms, and are struck the most often above 30,000ft by cloud to cloud lightning.

Most cloud to ground aircraft strikes occur when the aircraft is close to ground.

Yes you are correct as it is one of the many reasons they avoid storms, and strikes are rare

Even carbon fiber bodied aircraft are conductive, but I have seen photos of a hole in one caused by lightning, kind of shattered, but the plane made it back to Earth ok.

 

[dereckbc]

But how does an electrical system that is not connected to the earth, such as an aircraft, dissipate high voltage occurances such as lightning?

Simple is doesn't. The potential simply rises and falls. There is no path for current to flow.

As an example, don't try this, but imagime putting down a ruber insulating braket on the ground in front of your service panel, reach in and touch one of the phases. Nothing happens. Why? There is no path for current to flow.

Ground is a bad thing. Only electrical utilities and HV applications are allowed to use earth as a conductor. No other application is allowed to use earth as a conductor.

In a residential or an application less than 600 volts, earth or ground has no active part in clearing any electrical faults on the derived system. That is the job of the Equipment Ground Conductors and no connection to earth is required to do that. Ground is a terrible term to use. We use it to confuse the Russians, Chi-Coms, and the public. :grin:

 

[LarryFine]

Same reasons birds don't get zapped when they land on a wire: no current. They simply attain the same voltage as the wire.

 

[morgan01]

Hi

Hi

Most of the RV parks provide the space for aircraft to land safely. hence you can also hire an aircraft to visit the campgrounds.

 

[morgan01]

Aircraft & RV Grounding

Yes aircraft can be grounded in the RV parks as enough landing space is provided.

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[morgan01]

Aircraft & RV Grounding

Almost all the RV parks are provided wth enough space for the aircraft to land. hence this is definitely not an issue. you can directly come to these parks in your private helicopter or the aircraft if you wish.


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